Repurposing and Rescuing of Mibefradil, an Antihypertensive, for Cancer: A Case Study

The expanding "valley of death" in drug development is leaving potentially life-saving new chemical entities and molecular targets fallow. This situation is forcing early-stage companies to think creatively about moving their technologies forward, especially as institutional investors show more interest in later stages of development. Drug repurposing, a strategy to examine existing drugs for therapeutic value against different diseases, is an emerging method to bring an off-market drug back onto the market. Tau Therapeutics LLC identified the role of T-type calcium channel blockers (Cav3) in cancer proliferation, but the company was unable to attract funding while having both a nonvalidated drug target and new chemical entities. To change the risk profile of the company, Tau set out to repurpose the known Cav3 drug mibefradil as a proof of concept for the treatment of cancer. Mibefradil was launched for hypertension in the 1990s but withdrawn because of drug-drug interactions. A new sequential combination treatment, termed Interlaced Therapy™, uses short-term administration of mibefradil to enhance the overall therapeutic potential of conventional anticancer agents. Mibefradil is currently in a phase Ib clinical trial with the National Cancer Institute (NCI) Adult Brain Tumor Consortium. Mibefradil has been repurposed from an abandoned antihypertensive to a targeted solid tumor treatment, and it has been rescued from drug-drug interactions by using short-term dose exposure. Tau is using the early success of mibefradil as a proof of concept to build a platform technology of Cav3 blockers for broad antitumor applications in combination with new targeted cancer therapies, well-established chemotherapies, and radiation.